Powertrain operation and regulation

ABSTRACT

One or more powertrains can include a motor-generator disposed therein that is electrically coupled to an energy storage device through an inverter gate. A regulation strategy can monitor operation of the powertrain to regulate the inverter gate to selectively discharge energy from the energy storage device to the motor-generator to assist the powertrain or to charge energy from the motor-generator to the energy storage device for future use. In an aspect, the regulation strategy may maintain a consistent speed of an internal combustion engine associated with the powertrain. In another aspect, the regulation strategy may regulate simultaneous operation of first and second powertrains disposed a parallel relation.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.15/234,695 by Peter J. Miller et al., filed on Aug. 11, 2016, which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

This patent disclosure relates generally to regulating operation of oneor more powertrains in a machine and, more particular, to selectivelyconverting and utilizing kinetic energy and potential energy stored inan energy storage device to operate the powertrains.

BACKGROUND

A machine such as a construction or mining machine typically has apowertrain that includes the components that transmit and adjust thepower or energy output from the prime mover, such as an internalcombustion engine, to the point of utilization such as propelling themachine or operating implements associated with the machine. Powertraincomponents can include drive shafts, transmissions, differentials, powertakeoffs, and other components that are responsible for operation of themachine. The prime mover is the source or origin of the kinetic ormechanical energy transmitted through these components. An internalcombustion engine, for example, can combust a hydrocarbon-based fuel toconvert the chemical energy therein to kinetic energy or mechanicalpower embodied as the rotational motion of a driveshaft. Whiletraditional machines included a single prime mover as the source ofenergy, more recent hybrid designs may combine different technologies toprovide complementary sources of energy for the machine in order toimprove efficiency and prolong machine life.

One common hybrid technology is regenerative braking in which thepowertrain is configured to slow or stop the motion of the machine, orthe moving implements of the machine, by capturing and storing thekinetic energy associated with the motion. Regenerative braking cantherefore recover some of the applied braking power of the machine forreuse rather than dissipating the power through friction and heatgeneration. In a hydraulic hybrid design, the captured energy can bestored in the form of pressurized fluid in an accumulator that can laterbe reapplied as kinetic energy in the powertrain. An alternative designfor a hybrid powertrain is an electric hybrid system in which thecaptured energy is stored as electrical power in batteries or capacitorsfor further use such as to power electric motors associated with themachine. U.S. Pat. No. 7,565,801 describes a machine, such as anexcavator, which includes variations of a hydraulic hybrid system and anelectric hybrid system to capture and reuse kinetic energy associatedthe operation of the excavator. The present disclosure is similarlydirected to recovering and reusing the energy transmitted through one ormore powertrains associated with a machine such as an excavator.

SUMMARY

The disclosure describes, in one aspect, method of regulating operationof a powertrain having an internal combustion engine, a motor-generator,and a powertrain load coupled together in series. The method begins byoperating the internal combustion engine at a first engine speed. Anenergy storage device is electrically connected to a motor-generator andcan be charged through an inverter gate with electrical energy from themotor-generator. The method may register a change in the powertrain loadand determine if the change represents a torque change condition or aspeed change condition. If the change represents a torque changecondition, the method operates the inverter gate to maintain the firstengine speed. If the change represents a speed change condition, themethod operates the inverter gate to accelerate the internal combustionengine to a second engine speed.

In another aspect, the disclosure describes a powertrain for a machinehaving an internal combustion engine operable at a plurality of enginespeeds and a motor-generator physically coupled in series to theinternal combustion engine. The motor-generator capable of operating aseither a motor or a generator. A powertrain load is physically coupledin series to the motor-generator and the internal combustion engine. Tostore energy, an energy storage device is electrically coupled to themotor-generator through an inverter gate. To control operation of thepowertrain, a controller communicating with the inverter gate isprogrammed to register a change in the powertrain load and to determineif the change represents a torque change condition or a speed changecondition. The controller is further programmed to operate the invertergate to maintain a first engine speed of the internal combustion engineunder the torque change condition and to accelerate the internalcombustion engine under the speed change condition.

In yet a further aspect, the disclosure describes a method of regulatingoperation of a machine having a first powertrain and a second powertrainarranged in parallel. The method calculates the total power requirementof the machine based upon various inputs. The method divides the totalpower requirement between the first powertrain and the second powertrainto determine a first request signal and a second request signal. Thefirst request signal is converted to a first torque signal and thesecond request signal is converted to a second torque signal. The methoduse the first torque signal to determine a direction of energy flowbetween a first energy storage device electrically coupled to a firstmotor-generator of the first powertrain and uses the second torquesignal to determine a direction of energy flow between a second energystorage device electrically coupled to a second motor-generator of thesecond powertrain.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a machine in the embodiment ofan excavator having a first powertrain and a second powertrain, removedfrom the machine for illustration, each of which includes an internalcombustion engine and a motor-generator coupled in series and arrangedas a hybrid system in accordance with the disclosure.

FIG. 2 is a flowchart representing a regulating process that may beutilized to regulate the torque and speed produced in the first and/orsecond powertrains in accordance with an aspect of the disclosure.

FIG. 3 is a chart representing engine speed verses timing to graph theperformance of the powertrain when the regulating process attempts tochange the output torque while maintaining the speed of the internalcombustion engine.

FIG. 4 is a chart representing engine speed verses timing to graph theperformance of the powertrain when the regulating process attempts toassist increasing speed of the internal combustion engine.

FIG. 5 is a schematic block diagram representing a regulating processfor parallel operation of the first and second powertrains in accordancewith another aspect of the disclosure.

DETAILED DESCRIPTION

This disclosure relates to one or more powertrains configured to recoverand reuse the kinetic energy generated by a prime mover to assist inoperation of a machine. Referring to FIG. 1, wherein like referencenumbers refer to like elements, there is illustrated an embodiment of amachine 100 in accordance with the disclosure that specifically is inthe form of an excavator used for excavating and moving earth or othermaterials about a worksite. However, the disclosure may have broaderapplicability in various other types of machines as well. The term“machine” as used herein may refer to any machine that performs sometype of operation associated with an industry such as mining,construction, farming, transportation, or any other industry known inthe art. For example, the machine may be an earth-moving machine, suchas a wheel loader, excavator, dump truck, backhoe, motor grader,material handler or the like. Moreover, an implement may be connected tothe machine. Such implements may be utilized for a variety of tasks,including, for example, loading, compacting, lifting, brushing, andinclude, for example, buckets, compactors, forked lifting devices,brushes, grapples, cutters, shears, blades, breakers/hammers, augers,and others.

To interface with the work materials, the machine 100 includes anelongated boom 102 that at one end is pivotally connected to a similarlyelongated dipper or stick 104 such that the two components form anarticulating joint with each other. An opened mouthed bucket can bejoined by a hinge at an opposite end of the stick 104 that is configuredfor scooping and holding the material. The bucket 106 may have astraight cutting edge 108 opposite the hinged connection that includes aplurality of protruding teeth. The end of the boom 102 opposite thestick 104 is pivotally supported by and can articulate with respect toan upper structure 110 of the machine 100. The pivotal connectionsbetween the boom 102, stick 104, and bucket 106 enable the operator tolift, lower and otherwise maneuver the bucket with respect to the workmaterial. To forcibly articulate or actuate the pivotally linkedcomponents, the boom 102, stick 104, and bucket 106 may be operativelyassociated with one or more telescoping hydraulic cylinders forming partof the hydraulic system of the machine 100.

To accommodate the operator, the upper structure 110 can include anoperator's cab 112 disposed in a position providing visibility about theworksite and inside of which various machine motion controls, powerplant controls, gauges, and readouts are located. The upper structure110 can also accommodate the components of the power system, hydraulicsystem, and other systems associated with the machine. These systemsalso provide the upper structure 110 with additional mass orcounterweight to balance the digging and lifting operations of the boom102, stick 104, and bucket 106. To further facilitate digging andloading operations, the upper structure 110 of the machine 100 can bepivotally mounted on an undercarriage 114 such that the upper structurecan swing the boom 102 and stick 104 horizontally around for loading ordumping loads from the bucket 106. To propel the machine 100 over theground or surface of the worksite, the undercarriage 114 can be equippedwith a plurality of continuous tracks 116; however, in otherembodiments, the machine may utilize solid or pneumatic wheels or otherpropulsion devices.

As can be appreciated from the foregoing, the machine 100 can performseveral different operations. Some operations may be energy intensive,such as lifting and driving the bucket 106 through the work material.Other operations may require relatively less energy, such as propellingthe machine about a worksite, but necessitates that the continuoustracks 116 or other propulsion devices operate at significant speeds.The machine 100 may readily switch between such energy or speedintensive operations.

To generate energy to propel the machine 100 and operate its associatedequipment, a powertrain 120 can be included that, in FIG. 1, isillustrated as removed from the upper structure 110. In accordance withthe disclosure, the powertrain 120 is configured as a diesel- orgas-electric hybrid system that can utilize both hydrocarbon-based fuelsand electric power. To combust hydrocarbon fuels, the powertrain 120includes a prime mover in the form of an internal combustion engine 122such as a diesel-burning, compression ignition engine, although otherengine configurations can be utilized with the disclosed powertrain. Theinternal combustion engine 122 burns fuel and converts the chemicalenergy therein into kinetic or mechanical force, specifically torquemeasured in foot-pounds or newton-meters, that is transferred from theengine by a rotating output or driveshaft 124. The rotational speed ofthe driveshaft 124 can be measured in revolutions per minute (RPM).

To provide the electrical component of the hybrid powertrain 120, amotor-generator 126 is operatively connected in series with thedriveshaft 124 from the internal combustion engine 122. Themotor-generator 126 can be an electromechanical device that is capableof operating as either a motor converting electricity to kinetic ormechanical energy or conversely as a generator converting mechanicalenergy into electricity. The motor-generator typically includes arotator made of coils, windings or the like that is rotatably disposedin a stationary stator of similar electrical construction by, forexample, ball bearings. Relative motion of the rotator and stator andthe interaction of electromagnetic forces carried by those componentscan alternatively generate an electrical charge or mechanical rotation.To mechanically couple with other components, the motor-generator 126can include an output shaft 128 protruding from the opposite side thatis coupled to the driveshaft 124. The motor-generator 126 can operate oneither alternating current (AC) or direct current (DC), thoughalternating current may be more practicable for the intendedapplication.

The powertrain 120 may be coupled to a powertrain load associated withthe machine that utilizes the output of the powertrain. For example, inan embodiment, the functions of the machine 100 may be primarilyhydraulically actuated including the lifting, swinging, and propulsionfunctions. Accordingly, the powertrain 120 may be operatively associatedwith a hydraulic system and may be used to operate one or more hydraulicpumps 130. The hydraulic pump 130 is coupled to the output shaft 128from the motor-generator and can generate hydraulic pressure that causesa hydraulic fluid to flow within the hydraulic system. Hoses or conduitscan direct the hydraulic fluid to different actuators disposed about themachine and associated with the hydro-mechanical components of themachine. In other embodiments, however, the output shaft 128 may bephysically linked to other components such as the continuous tracks 116to power their operation directly with the generated torque output.

As indicated above, under certain operating conditions, themotor-generator 126 may operate as a generator generating electric poweror energy from the kinetic energy input from the internal combustionengine 122. To temporarily store the electrical energy as potentialenergy for future use, the motor-generator 126 may be operativelyassociated with an energy storage device 132. The energy storage device132 may be a capacitor or rechargeable battery electrically coupled tothe motor-generator by conductive wiring or the like. As known to thoseof skill in the art, a capacitor can store electric energy in anelectric field while a battery can store chemical potential energy.Because both types of energy storage operate on DC power, and themotor-generator 126 typically generates AC power, an inverter gate 134can be disposed between the motor-generator 126 and the energy storagedevice 132. The inverter gate 134 can convert the energy between DCpower and AC power and may be electronic or electromechanical inconfiguration. In addition to converting between power types, theinverter gate 134 may function as a directional switch between themotor-generator 126 and the energy storage device 132 and canselectively direct the flow of energy between the two components.

In a particular further embodiment of the disclosure, the machine 100may include a second powertrain 140 similar in configuration to thefirst powertrain 120 and illustrated schematically below the firstpowertrain. Accordingly, the second powertrain 140 can include a secondinternal combustion engine 142 physically coupled in series to a secondmotor-generator 146 via a driveshaft 144 with the second motor-generatorcoupled in series to a second hydraulic pump 150 via an output shaft148. To enable the second powertrain 140 to operate as a hybrid system,the second power train can also be operatively associated with an energystorage device 152 that is electrically coupled to the secondmotor-generator 146. To selectively switch the direction of energy flowbetween the second motor-generator 146 and the second energy storagedevice 152, a second inverter gate 154 can be disposed between thecomponents. The first and second powertrains 120, 140 can be physicallyarranged in parallel with each other on the machine 100 and can sharethe task of providing power for the various systems and functions of themachine. In various embodiments, the size and performancecharacteristics of the first and second internal combustion engines, andthus the first and second powertrains, may be the same or different andeach may operate at different power or speed requirements as explainedbelow.

To coordinate and control the various components in the first and secondpowertrains 120, 140, the machine 100 may include an electronic orcomputerized control unit, module or controller 160. The controller 160may be adapted to monitor various operating parameters and toresponsively regulate various variables and functions affecting thepowertrain. The controller 160 may include a microprocessor, anapplication specific integrated circuit (ASIC), or other appropriatecircuitry and may have memory or other data storage capabilities.Although in FIG. 2, the controller 160 is illustrated as a single,discrete unit, in other embodiments, the controller and its functionsmay be distributed among a plurality of distinct and separatecomponents. To receive operating parameters and send control commands orinstructions, the controller 160 may be operatively associated with andmay communicate with various sensors and controls associated with thevarious components in the powertrains 120, 140. Communication betweenthe controller 160 and the sensors and controls may be established bysending and receiving digital or analog signals across electroniccommunication lines or communication busses. The various communicationand command channels are indicated in dashed lines for illustrationpurposes with the controller 160 specifically communicating with theinternal combustion engines 122, 142, the motor-generators 126, 146, theenergy storage devices 132, 152, and the inverter gates 134, 154. Inaddition, the controller 160 can communicate with the other componentsand systems on the machine 100 and even interface with an operator inthe operator's cab 112.

Referring to FIG. 2, there is illustrated a flowchart of a possibleroutine or process 200 for regulating the transmission of torque and/orspeed, i.e., kinetic energy, through either or both of the first andsecond powertrains as the machine proceeds through various maneuvers,some which may require increased power output and others which mayrequire prompt speed response. The controller associated with themachine can be configured to conduct the regulating process by executionof stored software. By way of example, the regulating process 200 maybegin with an initial engine speed step 202 in which the internalcombustion engine operates at a first engine speed. In machines of theforegoing type, it may be desirable to maintain operation of theinternal combustion engine at a constant speed or within a relativelysmall speed band to improve efficiency and simplify operation of theassociated hydraulic system. Accordingly, during the initial enginespeed step 202, the regulating process 200 can attempt to maintain aconsistent speed of the internal combustion engine. In a monitoring step204, the regulating process 200 monitors the powertrain load on thepowertrain that can include any digging, lifting, propulsion, or swingoperations the machine may be undertaking. The monitoring step 204 canbe accomplished by sensing pressure feedback on the hydraulic system,transmission loads, operator requests and similar variables.

In a registration step 206, the regulating process 200 can register achange in the powertrain load applied to or requested of the powertrain.To determine the status of the registered load change, the regulatingprocess can conduct a load determination step 208 in which the processdecides if the registered load change represents a change in the requesttorque output of the machine (i.e. a torque change condition) or achange in the requested speed output (i.e. speed change condition) ofthe machine. The torque change condition and speed change condition canbe associated with different maneuvers performed by the machine. Theload determination step 208 can be based upon information received fromsensors associated with the different machine systems communicatingvariables associated with or representative of the different operationsto the controller.

If, for example, and with reference to FIGS. 1 and 2, the loaddetermination step 208 determines the registered load change representsa request for a change in the torque output, the regulating process 200can conduct a subsequent torque determination step 210 that determinesif the torque output request represents a request for increased torqueoutput (i.e. torque increase condition) or decreased torque output (i.e.decreased torque condition) of the first powertrain 120. For instance,if the machine 100 is conducting a load intensive operation such asdigging into or lifting material, it will be appreciated the powertrain120 needs to quickly increase torque output to provide the requiredkinetic energy and power for the operation. However, if the machine 100is performing a braking operation or low power intensity operation suchas lowering the bucket, the torque output required of the powertrain 120correspondingly decreases. The regulating process 200 consequentlyoperates the powertrain in accordance with the outcome of the torquedetermination step 210.

For example, if the torque determination step 210 determines a torqueincrease is required, the regulating process 200 can regulate the flowof energy in the hybrid powertrain 120 to assist in providing additionenergy. More specifically, as load increases on the powertrain 120, theinternal combustion engine 122 will tend to lug or slow down to maintainperformance. Lugging the internal combustion engine 122 may have adverseconsequences for the internal combustion engine such as increased wearor overheating. To address this, the process 200 can perform a dischargestep 212 in which the stored potential energy in the energy storagedevice 132 is directed back to the powertrain 120. Specifically, theinverter gate 134 operates to discharge stored potential energy in theform of electricity from the energy storage device 132 to themotor-generator 126 where the electricity is converted to kinetic energyin the form of rotational torque. The torque is transmitted from themotor-generator 126 to the internal combustion engine 122 to assist theengine and prevent lugging or unintentional slowing.

In the alternative, if the torque determination step 210 determines thatthe powertrain 120 has excess torque for the applied load, i.e., themachine 100 is performing a low intensity operation; the regulatingprocess 200 can operate the powertrain to reduce the torque as part of atorque decrease condition. For example, if machine 100 is attempting tobrake or slow down, the momentum of the machine may be directed backthrough the powertrain causing an overspeed condition to occur in theinternal combustion engine 122 running the engine faster than intended.The overspeed condition may similarly result in wear and overheating. Toaddress the overspeed condition, the regulating process 200 can conducta charge step 214 that utilizes the motor-generator 126 to charge theenergy storage device 132, specifically, by converting the excess torquebeing transmitted in the motor-generator into electrical energy. Theinverter gate 134 operates to direct the electrical energy to the energystorage device 132 for storage as potential energy. The charging step214 effectively applies an additional torque load to the internalcombustion engine that directs or removes kinetic energy from thepowertrain 120 for future use, for example, in a subsequent dischargestep 212.

A result of this aspect of the regulating process 200 maintains theengine speed of the internal combustion engine with a degree ofconsistency during load changes as part of a maintain engine speed step216 of the process. Referring to FIG. 3, a chart 300 illustratesperformance of the powertrain 120 with and without assistance of theinteraction between the motor-generator 126 and energy storage device132. In FIG. 3, the Y-axis 302 represents the actual engine speed of theinternal combustion engine 122 in revolutions per minute (RPM), theX-axis 304 represents time in seconds, the first curve 306 representsoperation of the engine without energy recovery and the second curve 308represents operation with energy recovery. In accordance with theregulating process 200, the internal combustion engine 122 may initiallyoperate at a consistent speed during the initial engine speed step 202,as indicated by the horizontal overlap of the first and second curves306, 308. However, if the torque demand on the powertrain 120 increases,it could lug or slow the internal combustion engine down as indicated bythe speed dip 312 in the first curve 306. Likewise, if the torquedemanded of the powertrain 120 drops, the internal combustion engine 122may go into an overspeed condition as indicated by the speed rise 314 inthe first curve. With the regulating process 200, by introducingadditional torque into the powertrain 120 through the discharge step 212or by removing torque from the powertrain through the charge step 214,the internal combustion engine maintains a consistent engine speed asindicated by the second curve 308.

In another aspect, if the load determination step 208 determines theregistered load change indicates a requested change in the speed outputof the powertrain 120, i.e., the speed change condition, the regulatingprocess 200 can assist the powertrain in increasing engine speed.Specifically, in a second discharge step 220, the inverter gate 134 mayoperate to discharge electrical energy from the energy storage device132 to the motor-generator 126 that converts the electrical energy tokinetic energy in a manner that increases or accelerates the speed ofthe motor-generator. Relatedly, this increases or accelerates the enginespeed of the internal combustion engine 122 to a second engine speed inan accelerate engine speed step 222. Once accelerated, the internalcombustion engine 122 can be maintained at the second engine speed in asecond maintain engine speed step 224, thereby effectively raising thespeed of the powertrain 120. During the second maintain engine speedstep 224, while the internal combustion engine is operating in a steadystate manner at the consistent second engine speed, the regulatingprocess 200 can operate the inverter gate 134 to divert a portion of theelectric power in the motor-generator 126 to charge the energy storagedevice 132 in a second charge step 226 thereby recovering energy forfuture use.

The effect of assisting the internal combustion engine 122 during speedchange conditions can be seen in FIG. 4, which is a chart 350 similar toFIG. 3 illustrating operation of the internal combustion engine with andwithout assistance from the motor-generator 132. In FIG. 4, the Y-axis352 represents engine speed in RPM and the X-axis 354 represents time inseconds. The first curve 356 shows response time of the internalcombustion engine 122 without assistance from the motor-generator 126while second curve 358 depicts response time with such assistance. Thefirst curve 356 is denoted by periods of delay indicated by the moderateslope 360 at the times the first curve 356 rises in speed. The secondcurve 358 in contrast depicts much sharper slopes 362 during theseengine speed increases, reflecting the assistance provided bydischarging electrical energy from the energy storage device 132 to themotor-generator 126.

Referring to FIG. 2 and FIG. 5, there is illustrated another embodimentof a regulating process 400 in the form of a block diagram forregulating operation of those embodiments of the machine 100 havingfirst and second powertrains 120, 140 operating in parallel. Similar tothe process described in FIG. 2, the regulating process 400 can beexecuted by the controller associated with the machine in conjunctionwith the information obtained through sensors, controls and the like. Inan initial series of monitoring operations 402, the regulating process400 can obtain or receive operator commands 404 or inputs regardingrequested speed or torque and performance information 406 or feedbacksuch as hydraulic pressures, flows, combusting efficiency etc. Theregulating process 400 can use the operator commands 404 and performanceinformation 406 to perform power calculations 408 that calculate thetotal machine power required to achieve the desired operation of themachine. The power calculations 408 may additionally use anticipatoryperformance variables or predicative routines to anticipate futuremachine power requirements.

In a subsequent series of operations, the regulating process 400 candivide the total machine power requirements determined by the powercalculations 408 between the first and second powertrains 120, 140 onthe machine 100. For example, in an engine determination step 410, theprocess can decide whether output from the first internal combustionengine 122, the second internal combustion engine 142, or both aredesired or necessary to provide the calculated total machine powerrequirements. Some operations may require the energy output from onlyone powertrain verses both, while other operations may be betterperformed by one powertrain verses the other due to the specificequipment or characteristics associated with the particular powertrain.The regulating process 400 can also execute a speed determination step412 that determines the engine speed request required of the first andsecond internal combustion engines 122, 142 in each of the powertrains120, 140 to meet the machine power requirements calculated by the powercalculations 408. In a request transmission step 414, the regulatingprocess 400 develops an electronically transmittable and executablefirst request signal 416 and second request signal 418 associated witheach of the first and second powertrains 120, 140.

Because the first and second internal combustion engines 122, 142 may becurrently operating when the power calculations 408 are performed, thedetermined first request signal 416 and second request signal 418representing the total machine power requirements may not beappropriate. In other words, because the first and second internalcombustion engines 122, 142 may be running at existing engine speedswhen the request signals 416, 418 are received, the regulating process400 can perform a discrepancy determination step 420 to calculate thediscrepancy. In particular, the discrepancy determination step 420 canreceive the first existing engine speed 422 associated with the firstinternal combustion engine 122 along with the first request signal 416and utilize arithmetic to calculate a first discrepancy signal 424reflecting the actual speed change required to meet the calculated totalpower requirements for the machine. Likewise, the discrepancydetermination step 420 can receive a second existing engine speed 426 ofthe second internal combustion engine 142 with the second request signal418 to calculate a second discrepancy signal 428. The first and seconddiscrepancy signals may or may not be equal depending upon the relativeoperational conditions or performance of the first and second internalcombustion engines 122, 142.

After the first and second discrepancy signals 424, 428 have beendetermined, the first and second powertrains 120, 140 can be operatedaccordingly. In the present embodiment, where the first and secondpowertrains 120, 140 include respective first and secondmotor-generators 126, 146 to assist operation of the first and secondinternal combustion engines 122, 142, the regulating process 400 canconduct a torque determination step 430 similar to the process describedwith respect to FIG. 2. For example, the torque determination step 430may determine what the desired torque output of the respective first andsecond powertrains 120, 140 is, or in other words, what the kinematicenergy transferred through the powertrains is needed. The torquedetermination step 430 can result in a first torque signal 432 andsecond torque signal 434, which may or may not be equal in quantity. Theregulating process 400 utilizes the first and second torque signals 432,434 to operate the respective powertrains 120, 140 appropriately. Thismay include determining whether to operate the first and second invertergates 134, 154 to direct torque to or from the respective powertrains120, 140 in an inverter control step 440. For example, the invertercontrol step 540 may dictate the direction of electricity flowingbetween the energy storage device 132, 152 and the motor-generators 126,146 to charge or discharge the storage devices. The inverter controlstep 440 may operate the inverter gates 134, 154 independently with thefirst charge the energy storage device 132 and the second dischargingthe storage device 152 as appropriate of the respective first and secondtorque signals 432, 434.

INDUSTRIAL APPLICABILITY

The disclosure can assist in regulating torque and speed transmission ina powertrain 120 by utilizing a hybrid architecture to accommodate thedifferent operations undertaken by the machine 100 such as an excavator.The powertrain 120 includes a motor-generator 126 physically disposedbetween an internal combustion engine 122 and a varying powertrain loadproduced by the machine 100. The motor-generator 126 is configured toconvert kinetic energy in the form of rotational torque to storableelectrical energy, i.e., potential energy, and vice versa. To store theelectrical energy, the motor-generator 126 is electrically coupled to anenergy storage device 132. To selectively charge electric energy to anddischarge electrical energy from energy storage device 132, an invertergate 134 is disposed between the storage device 132 and motor-generator126.

The disclosure further provides a regulating process 200 to regulateoperation of the powertrain during different operational conditions ofthe machine 100. For example, during energy intensive operations such aslifting or digging, the regulating process 200 attempts to maintain aconsistent engine speed of the internal combustion engine 122 whileaccommodating the varying torque requirement in the powertrain 120. Thiscan be accomplished by operating the inverter gate 134 to selectivelycharge energy to and discharge energy from the energy storage device132. The energy storage device 132 and inverter gate 134 thus act asspeed control device for the internal combustion engine 122. Duringspeed intensive operations, the regulating process 200 regulates thepowertrain 120 to assist in accelerating the internal combustion engine122 also by selectively directing energy to and from the energy storagedevice 132.

In another aspect, the regulating process 400 can simultaneouslyregulate first and second powertrains 120, 140 arranged in parallel in amachine 100. The regulating process 400 can divide the total machinepower requirements and independently operate first and second energystorage devices 132, 152 associated with the respective powertrains toproduce torque or speed values having the same or different quantitiesdepending on the total power requirements of the machine. These andother possible advantages of the disclosure should be apparent from theforegoing description and figures.

It will be appreciated that the foregoing description provides examplesof the disclosed system and technique. However, it is contemplated thatother implementations of the disclosure may differ in detail from theforegoing examples. All references to the disclosure or examples thereofare intended to reference the particular example being discussed at thatpoint and are not intended to imply any limitation as to the scope ofthe disclosure more generally. All language of distinction anddisparagement with respect to certain features is intended to indicate alack of preference for those features, but not to exclude such from thescope of the disclosure entirely unless otherwise indicated.

Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context.

The use of the terms “a” and “an” and “the” and “at least one” andsimilar referents in the context of describing the invention (especiallyin the context of the following claims) are to be construed to coverboth the singular and the plural, unless otherwise indicated herein orclearly contradicted by context. The use of the term “at least one”followed by a list of one or more items (for example, “at least one of Aand B”) is to be construed to mean one item selected from the listeditems (A or B) or any combination of two or more of the listed items (Aand B), unless otherwise indicated herein or clearly contradicted bycontext.

Accordingly, this disclosure includes all modifications and equivalentsof the subject matter recited in the claims appended hereto as permittedby applicable law. Moreover, any combination of the above-describedelements in all possible variations thereof is encompassed by thedisclosure unless otherwise indicated herein or otherwise clearlycontradicted by context.

We claim:
 1. A method of regulating operation of a machine comprising:calculating a total power requirement of the machine based upon inputs;dividing the total power requirement between a first powertrain and asecond powertrain to determine a first request signal and a secondrequest signal; converting the first request signal to a first torquesignal and converting the second request signal to a second torquesignal; using the first torque signal to determine a direction of energyflow between a first energy storage device electrically coupled to afirst motor-generator of the first powertrain; and using the secondtorque signal to determine a direction of energy flow between a secondenergy storage device electrically coupled to a second motor-generatorof the second powertrain.
 2. The method of claim 1, wherein the step ofdetermining a direction of energy flow results in one of charging ordischarging the first energy storage device and charging or dischargingthe second energy storage device respectively.
 3. The method of claim 2,wherein the step of determining a direction of energy flow operates afirst inverter gate disposed between the first energy storage device andthe first motor-generator and operates a second inverter gate disposedbetween the second energy storage device and the second motor-generator.4. The method of claim 3, further comprising the step of determining afirst deficiency signal representing a difference between a firstexisting engine speed and the first request signal; and determining asecond deficiency signal representing a difference between a secondexisting engine speed and the second request signal.
 5. The method ofclaim 4, further comprising determining whether output of a firstinternal combustion engine in the first powertrain, a second internalcombustion engine in the second powertrain, or both are required to meetthe total power requirement of the machine.